South Sudan's President Salva Kiir (left) and rebel leader Riek Machar (right) shake hands and pray before signing an agreement of the cease-fire of the South Sudan conflict on Friday in Addis Ababa, Ethiopia.

South Sudan's president has signed an agreement with a rebel leader that calls for the "immediate cessation of hostilities."

The United Nations has sent peacekeepers, and Secretary of State John Kerry traveled to the region to try to bring out about an end to the violence.

On Friday, after a face-to-face meeting in Addis Ababa, Ethiopia, the two sides came to an agreement.

Kenyan President Uhuru Kenyatta, who was mediating on behalf of the African Intergovernmental Authority on Development, said he was "very pleased."

"Today's events show that the region is committed to facilitating the return of peace and stability in an important neighbor and friend," Kenyatta said in a statement.

The Guardianreports that thousands of people have been killed and 1.3 million have been displaced since the violence broke out in December.

The paper adds:

"US national security adviser Susan Rice welcomed the peace agreement in a statement, saying it 'holds the promise of bringing the crisis to an end.'

"A ceasefire in January between South Sudan president Salva Kiir and rebel leader Riek Machar fell apart within days.

"Rice urged that Kiir and Machar follow up on the new peace deal signed in Addis Ababa, Ethiopia, by 'ending the violence and negotiating in good faith to reach a political agreement.' A statement by the spokesman for UN secretary-general Ban Ki-moon demanded that both sides 'immediately translate these commitments into action on the ground.' "